Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device has an interlayer insulation film formed on a first metal wiring and formed of an organic compound having a lower dielectric constant than that of SiO 2 , a second metal wiring formed on the interlayer insulation film, and an interlayer adhesion layer to improve adherence between the interlayer insulation film and the second metal wiring. The semiconductor device is provided with a stress buffer layer of which the elastic modulus is higher than that of the interlayer insulation film and is lower than that of the interlayer adhesion layer between the interlayer insulation film and the interlayer adhesion layer.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field of the Invention

[0002] The present invention relates to a semiconductor device and amethod of manufacturing the same, and more particularly to asemiconductor device having an interlayer insulation film having a lowerdielectric constant than that of SiO₂ and the method of manufacturingthe same.

[0003] 2. Description of the Related Art

[0004] To accomplish high speed and high integration of LSI, delay of asignal transmission speed caused by an electric capacity between wiringsand between interlayer insulation films has been problems. In thisregard, particularly in recent years, studies aiming for a lowdielectric constant of an interlayer insulation film have beenprogressed, and for example, organic compounds such as polyimidepolymer, bisbenzocyclobutene siloxane polymer (hereinafter referred toas “BCB”) are used as an interlayer insulation film. A specificdielectric constant of such organic compounds is about 1.5 to 2.5, andis greatly lower than that (about 4) of the conventional interlayerinsulation film mainly formed of SiO₂. In addition, it is possible thatthese organic compounds are easily deposited by spin coating andsintering and are deposited flat regardless of undulation of a basestructure.

[0005] However, in case of forming an interlayer insulation film by theorganic compounds, adherence to a metal used in wiring is weak, and theexfoliation tends to occur. Thus, in order to improve the adherence, aninterlayer adhesion layer has been provided between the interlayerinsulation film by the organic compounds and the wiring. For example, incase of using BCD as an interlayer insulation film, SiN and the like areused as an interlayer adhesion layer. Hereinafter, using thisembodiment, a structure of a semiconductor device will be explained withthe manufacturing method thereof.

[0006]FIG. 1 is a cross sectional view showing GaAs—IC using BCB as aninterlayer insulation film. In method of manufacturing the GaAs—IC,first, a first metal wiring 102 formed of Au, etc. and including adevice section such as FET is formed on a GaAs substrate 101 bysputtering method and dry etching method. Next, a first interlayeradhesion layer 103 formed of SiN is formed, for example, by plasma CVDmethod, etc. However, the first interlayer adhesion layer 103 can beomitted in case where sufficient adherence is obtained between the firstmetal wiring 102 and an interlayer insulation film 104 explained later.

[0007] Next, the interlayer insulation film 104 is formed of BCB and inthe thickness of 1,000 to 20,000 nm, for instance, by the steps ofcoating BCB in a desired thickness, and then, sintering and hardeningthe BCB under N₂ atmosphere at a temperature of 300° C. Then, a secondinterlayer adhesion layer 106 is formed of SiN by plasma CVD method.Next, a through hole 110 is formed by means of dry etching using aphotoresist mask (not shown). For example, SiN is etched by RIE using amixed gas of CF₄ and H₂, and BCB is etched by RIE using a mixed gas ofCF₄ and O₂. After that, a second metal wiring 108 formed of Au, etc. isformed by sputtering method, etc. Also, a protection layer (not shown)is formed to protect the second metal wiring 108. The protection layeris formed of SiN and the like, which have excellent adherence to thesecond metal wiring 108.

[0008] In addition, if the thickness of the SiN layer used in theinterlayer adhesion layer 103 and the protection layer 109 is thick, itcauses the specific dielectric constant to rise, thereby, it isdesirable to form the SiN layer to be about 50 to 100 nm as thin aspossible.

[0009] By the above-mentioned structure, an interlayer insulation filmin a semiconductor device can accomplish a low dielectric constant whilemaintaining excellent adherence to a metal wiring. However, there is abig difference in a mechanical characteristic between the organiccompound used as an interlayer insulation film and a material such asSiN used as an interlayer adhesion layer. For example, regarding aninterlayer insulation film of 5 μm in thickness using BCB and aninterlayer adhesion layer of 0.3 μm in thickness using SiN, the stressand elastic modulus thereof are shown in Table 1. In Table 1, a mark “+”and a mark “−” added to the numerical value indicate a tensile stressand a compressive stress, respectively, and BCB and SiN have the tensilestress and the compressive stress, respectively. Also, there is a largedifference in the elastic modulus between BCB and SiN. Accordingly, incase of stacking the both, a strong stress occurs in the interfacebetween them, so that brittle fracture tends to occur in SiN side havinghigher elastic modulus, and reliability of the semiconductor device isgreatly damaged. TABLE 1 BCB (organic film) SiN (the second film) (5 μm)(0.3 μm) Stress +37 −540 (MPa) Elastic modulus 2 320 (GPa)

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide a semiconductordevice using an organic compound having a lower dielectric constant thanthat of SiO₂ as an interlayer insulation film which has high reliabilitywithout fracture by stress concentration while maintaining adherencebetween said interlayer insulation film and the metal wiring and methodof manufacturing the same.

[0011] According to one aspect of the present invention, there isprovided a semiconductor device comprising: a first metal wiring; aninterlayer insulation film formed on the metal wiring and formed of anorganic compound having a lower dielectric constant than that of SiO₂; asecond metal wiring formed on said interlayer insulation film; aninterlayer adhesion layer formed to improve adherence between saidinterlayer insulation film and said second metal wiring; and a stressbuffer layer formed between said interlayer insulation film and saidinterlayer adhesion layer and having the elastic modulus higher thanthat of said interlayer insulation film and lower than that of saidinterlayer adhesion layer.

[0012] According to the semiconductor device of the present invention,it is preferred that said interlayer insulation film is formed of abisbenzocyclobutene siloxane polymer and said interlayer adhesion layeris formed of SiN, said stress buffer layer being formed of SiO₂. Withthis, in the semiconductor device using an organic compound as aninterlayer insulation film, it is possible to prevent brittle fractureby the stress concentration while maintaining adherence between themetal wiring and the interlayer insulation film, so that reliability ofthe semiconductor device is improved.

[0013] According to another aspect of the present invention, there isprovided a method of manufacturing a semiconductor device comprising thesteps of: forming an interlayer adhesion layer on a first metal wiring;forming a stress buffer layer of which the elastic modulus is lower thanthat of said interlayer adhesion layer on said interlayer adhesionlayer; forming an interlayer insulation film of which the elasticmodulus is lower than that of said stress buffer layer and which isformed of an organic compound having a lower dielectric constant thanthat of SiO₂ on said stress buffer layer; and forming a second metalwiring on said interlayer insulation film. With this, in thesemiconductor device using an organic compound as an interlayerinsulation film, it is possible to prevent brittle fracture by thestress concentration while maintaining adherence between the metalwiring and the interlayer insulation film, so that reliability of thesemiconductor device is improved.

[0014] According to the method of manufacturing the semiconductor deviceof the present invention, it is preferred that said stress buffer layeris formed by any one of thermal CVD method, plasma CVD method andoptical CVD method. With this, in the semiconductor device using anorganic compound as an interlayer insulation film, it is possible toprevent brittle fracture by the stress concentration while maintainingadherence between the metal wiring and the interlayer insulation film,so that reliability of the semiconductor device is improved.

[0015] According to the method of manufacturing the semiconductor deviceof the present invention, it is preferred that said interlayerinsulation film is a bisbenzocyclobutene siloxane polymer film formed bysequentially performing spin coating, and sintering and hardening stepsand said interlayer adhesion layer is SiN film formed by any one ofthermal CVD method, plasma CVD method and optical CVD method, saidstress buffer layer being SiO₂ film formed by any one of thermal CVDmethod, plasma CVD method and optical CVD method. With this, in thesemiconductor device using an organic compound as an interlayerinsulation film, it is possible to prevent brittle fracture by thestress concentration while maintaining adherence between the metalwiring and the interlayer insulation film, so that reliability of thesemiconductor device is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above objects, other objects, features and advantages of thepresent invention will be better understood from the followingdescription taken in conjunction with the accompanying drawings, inwhich:

[0017]FIG. 1 is a cross sectional view showing an embodiment of asemiconductor device according to the prior art;

[0018]FIGS. 2A through 2F are cross sectional views sequentially showinga method of manufacturing a semiconductor device according to the firstembodiment of the present invention;

[0019]FIG. 3 is a cross sectional view showing a semiconductor deviceaccording to the second embodiment of the present invention; and

[0020]FIG. 4 is a cross sectional view showing a semiconductor deviceaccording to the third embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a semiconductor device and a method of manufacturingthe same according to the embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

[0022] The first embodiment of the present invention will be explainedbelow. FIGS. 2A through 2F show a semiconductor device according to thefirst embodiment of the present invention, and are cross sectional viewssequentially showing a constitution of GaAs—IC using BCB as aninterlayer insulation film.

[0023] Referring to FIG. 2E, a first metal wiring 102 including a devicesection such as FET, a first interlayer adhesion layer 103, aninterlayer insulation film 104 formed of BCB in the thickness of about1,000 to 20,000 nm which has a lower dielectric constant than that ofSiO₂, a stress buffer layer 105, a second interlayer adhesion layer 106,a second metal wiring 108, and a protection layer 109 are sequentiallystacked on a GaAs substrate 101. The first metal wiring 102 and thesecond metal wiring 108 are formed of Au, etc. Also, the firstinterlayer adhesion layer 103, the second interlayer adhesion layer 106and the protection layer 109 are formed of SiN, etc. having excellentadherence to a metal. Further, when the thickness thereof is too thick,it causes the specific dielectric constant to rise, thereby, it ispreferable that the layers are as thin as possible within the rangewhere sufficient adherence is obtained, and particularly, the thicknessis preferable to be about 50 to 100 nm.

[0024] The stress buffer layer 105 is a layer provided to buffer astress caused by the difference of the elastic modulus between theinterlayer insulation film 104 (BCB) and the second interlayer adhesionlayer 106 (SiN). Accordingly, the material of which the elastic modulusis higher than that of the interlayer insulation film 104 (BCB) andlower than that of the second interlayer adhesion layer 106 (SiN), forexample, SiO₂ is adequate. In addition, the stress buffer layer 105 ispreferable to be about 100 to 500 nm in thickness so as to sufficientlybuffer the stress and not to cause fracture therein. Referring to Table2, SiO₂ film of 0.3 μm causes compressive stress like SiN film, but itselastic modulus is lower than that of the SiN film and higher than thatof the BCB film. Accordingly, by using the SiO₂ layer as a stress bufferlayer 105, the brittle fracture in the second interlayer adhesion layer106 (SiN) which has been a problem conventionally is prevented, so thatthe reliability of the semiconductor device can be improved. TABLE 2 BCESiO₂ (organic SiN (buffer film) (second film) layer) (5 μm) (0.3 μm)(0.3 μm) Stress (MPa) +37 −540 −570 Elastic 2 320 70 modulus (GPa)

[0025] Next, a manufacturing method of the semiconductor deviceaccording to the present invention will be described below withreference to FIGS. 2A through 2F. As shown in FIG. 2A, the first metalwiring 102 is formed on a GaAs substrate 101. The first metal wiring 102is formed of a material such as Au, and for instance, is deposited bysputtering method, etc., and then, may be formed by performing a dryetching using a photolithography technology. Next, a first interlayeradhesion layer 103 is formed so as to maintain adherence between thefirst metal wiring 102 and an interlayer insulation film 104 explainedlater. For example, SiN is adequate for the first interlayer adhesionlayer 103, and may be formed by plasma CVD method. In addition, in casewhere sufficient adherence is obtained between the first metal layer 102and the interlayer insulation film 104, the first interlayer adhesionlayer 103 may be omitted.

[0026] Next, an interlayer insulation film 104 is formed of BCB. First,BCB is made in a desirable thickness by spin coating method, and then,for example, is hardened by a sintering step under N₂ atmosphere at atemperature of 300° C. The surface of the BCB film formed as suchbecomes flat regardless of base substrate shape and unevenness.

[0027] Next, a stress buffer layer 105 is formed. SiO₂ is adequate forthe stress buffer layer 105, and may be formed by plasma CVD method.Then, as shown in FIG. 2B, a second interlayer adhesion layer 106 isformed. For instance, SiN is adequate for the second interlayer adhesionlayer 106, and may be formed by plasma CVD method, etc.

[0028] Next, as shown in FIG. 2C, a through hole 110 is formed bysequentially dry-etching the second interlayer adhesion layer 106, thestress buffer layer 105, the interlayer insulation film 104 and thefirst interlayer adhesion layer 103 using a photoresist mask 107. Forexample, dry etching of SiN and SiO₂ can be performed by RIE using amixed gas of CF₄ and H₂, and dry etching of BCB can be performed by RIEusing a mixed gas of CF₄ and O₂.

[0029] Next, as shown in FIG. 2D, after removing the photoresist mask107, a second metal wiring 108 is formed, and as shown in FIG. 2E, aprotection layer 109 protecting the second metal wiring is formed, sothat the GaAs—IC according to the first embodiment of the semiconductordevice of the present invention is manufactured.

[0030] Next, a second embodiment of the present invention will bedescribed. In the present embodiment, as shown in FIG. 3, an upperwiring is further stacked on the semiconductor device according to thefirst embodiment. As shown in the first embodiment, it is possible thatan interlayer insulation film formed of BCB and an interlayer adhesionlayer formed of SiN are stacked, and as a result, the interlayerinsulation film of BCB can be easily made in a multilayer form. Inaddition, since the manufacturing method of a semiconductor device shownin FIG. 3 is the same as that of the first embodiment, the explanationthereof will be omitted. Further, it is needless to say that an upperwiring can be further stacked on the semiconductor device shown in FIG.3.

[0031] Next, a third embodiment of the present invention will beexplained. In addition, the present invention is not limited to theGaAs—IC shown here, and for example, similarly to a semiconductor deviceaccording to the third embodiment shown in FIG. 4, it is needless to saythat the present invention can be applied to not only a semiconductordevice having constitution that SiN film is acting as a capacitor in acapacitor portion 310 and a second interlayer adhesion layer 106 inother places, but also a semiconductor device having other constitutionthat an organic compound is used as an interlayer staking layer.Further, in case where organic compounds other than BCB, for example,polyimide compound, etc. are used as an interlayer insulation film, thesame effect can be obtained by providing a stress buffer layer betweenthe interlayer insulation film and the interlayer adhesion layer,wherein the elastic modulus of the stress buffer layer is between thoseof the interlayer insulation film and the interlayer adhesion layer.

[0032] According to the present invention as described above, it ispossible to provide the semiconductor device using an organic compoundof a low dielectric constant as an interlayer insulation film which hashigh reliability without fracture by the stress concentration whilemaintaining adherence to the metal wiring and the method ofmanufacturing the same.

[0033] Although the technical spirits of the present invention has beendisclosed with reference to the appended drawings and the preferredembodiments of the present invention corresponding to the drawings, thedescriptions in the present specification are only for illustrativepurpose, not for limiting the present invention.

[0034] Also, those who are skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible withoutdeparting from the scope and spirit of the present invention. Therefore,it should be understood that the present invention is limited only tothe accompanying claims and the equivalents thereof, and includes theaforementioned modifications, additions and substitutions.

What is claimed is:
 1. A semiconductor device, comprising: a first metalwiring; an interlayer insulation film formed on the metal wiring andformed of an organic compound having a lower dielectric constant thanthat of SiO₂; a second metal wiring formed on said interlayer insulationfilm; an interlayer adhesion layer formed to improve adherence betweensaid interlayer insulation film and said second metal wiring; and astress buffer layer formed between said interlayer insulation film andsaid interlayer adhesion layer and having the elastic modulus higherthan that of said interlayer insulation film and lower than that of saidinterlayer adhesion layer.
 2. A semiconductor device according to claim1, wherein said interlayer insulation film is formed of abisbenzocyclobutene siloxane polymer, said interlayer adhesion layer isformed of SiN, and said stress buffer layer is formed of SiO₂.
 3. Amethod of manufacturing a semiconductor device, comprising the steps of:forming an interlayer adhesion layer on a first metal wiring; forming astress buffer layer of which the elastic modulus is lower than that ofsaid interlayer adhesion layer on said interlayer adhesion layer;forming an interlayer insulation film of which the elastic modulus islower than that of said stress buffer layer and which is formed of anorganic compound having a lower dielectric constant than that of SiO₂ onsaid stress buffer layer; and forming a second metal wiring on saidinterlayer insulation film.
 4. A method of manufacturing a semiconductordevice according to claim 3, wherein said stress buffer layer is formedof any one of thermal CVD method, plasma CVD method and optical CVDmethod.
 5. A method of manufacturing a semiconductor device according toclaim 3, wherein said interlayer insulation film is bisbenzocyclobutenesiloxane polymer film formed by sequentially performing spin coating,and sintering and hardening steps and said interlayer adhesion layer isSiN film formed by any one of thermal CVD method, plasma CVD method andoptical CVD method, said stress buffer layer being SiO₂ film formed byany one of thermal CVD method, plasma CVD method and optical CVD method.